The present invention is directed to a flexographic printing apparatus, and more particularly to a flexographic printing apparatus having an electric charging unit to enhance print quality.
A conventional flexographic printing press is typically provided with a plurality of printing stations, each of which prints a moving web with an image in a respective color. Each of the printing stations is provided with a rotating cylindrical ink roller, also referred to as an "anilox" roller, having a regular pattern of minute recesses or ink cells formed therein. Ink is applied to the ink roller by submerging at least a portion of the ink roller in an ink reservoir, or by applying ink to a portion of the ink roller via an ink applicator.
A flexographic press has a rotating cylindrical printing roller disposed adjacent the ink roller. The printing roller has a printing plate mounted thereon. The printing plate may be held in place on the printing roller by an adhesive layer, such as adhesive tape, disposed between the printing plate and the printing roller. The printing plate is composed of a photosensitive material that is subjected to a photo-etching process to form raised portions on the printing plate which correspond to a desired image to be printed. The printing roller is disposed adjacent the ink roller so that ink is transferred from the ink cells in the ink roller to the raised areas on the printing plate.
U.S. Pat. No. 4,697,514 to George, et al. discloses a gravure printing apparatus having a gravure cylinder that is disposed partially within an ink reservoir, a backing roller disposed adjacent the gravure cylinder, and an apparatus for applying a voltage to the backing roller. As shown in FIG. 7 of the George, et al. patent and described in connection therewith, the application of the voltage to the backing roller causes ink within the ink cells to rise above the surface of the gravure cylinder in order to enhance the ink transfer from the gravure cylinder to a paper web being printed.